Information storage disks, sometimes known as hard disks are typically made of aluminum and are typically subjected to a nickel-phosphorous plating step and a subsequent coating step using various thin film magnetic alloys, such as sputtered or vapor deposited alloys of cobalt, chromium, nickel and platinum or other cobalt alloys deposited on the disk, as seen in U.S. Pat. Nos. 5,180,640, 4,786,564 and 4,988,578 and in the prior art referenced in these patents. In normal practice the original disk blank surface is ground and following the NiP plating step, the blank is polished and cleaned to insure a smooth surface for reception of the magnetic alloy.
Most operations and processing steps in the production of storage disks have been automated including the use of robotic mechanisms for loading and unloading disks into and from a cassette and into a disc carrier for plasma or sputter magnetic particle coating of the disks. Prior to the coating step, it is necessary to grind the disk blank surface to arrive at an acceptable surface finish. Following grinding and a typical plating of NiP a subsequent polishing step is performed to arrive at a final surface finish suitable for a subsequent magnetic particle coating step. A typical apparatus for grinding and then polishing the disk has been an apparatus Model 9B14P available from SPEEDFAM Inc. of Chicago, Ill. This apparatus comprises a top platen for mounting various grinding or polishing equipment and a bottom platen onto which disks are manually placed and manually removed from a rotating carrier at the grinding or polishing station.
In another system, known as the Seiko-Systems grinder/polisher automated system, disks are loaded in a carrier, the carrier is moved to a grinder or polisher station, and after grinding or polishing the carrier is moved to an unload station.
FIG. 1 schematically illustrates the prior art SPEEDFAM-type apparatus where cassettes are filled with disk blanks, typically aluminum disks of 130 mm, 95 mm or 65 mm in diameter with a bevelled central aperture of 25 mm diameter (for a 95 mm disk) and a thickness of 31.5 mil (for a 95 mm disk), in cassette slots. The cassettes (not shown) are moved into the vicinity of the apparatus including a grinder or polisher 10 and removed by a worker from the cassette into a circular three-disk holder 12 positioned in depressions 14 on the holders 12 which holders are rotatively drivable by gear teeth 15 on the inner periphery of a ring gear 17 and gear teeth 19 (FIG. 2) on the periphery of the holders 12 and by gear teeth 13a on a sun gear 13. Only a few gear teeth are shown but it is to be understood that the gear teeth extend 360.degree. around each gear and holder. A center support column 13b supports the SPEEDFAM mechanism. Each disk is manually placed in a circular disk-receiving depression or recess 16 in each disk holder and after all the disk positions, for example, three positions in each of fourteen holders, for a total of forty-two disks, have been manually loaded, the appropriate grinding or polishing cycle is commenced. A control box 8 is mounted on platen 45. Each disk is ground or polished as each set of three disks are rotatively moved under a grinder or polisher depending from the top platen. Grinding or polishing occurs in the presence of a pumped supply (not shown) of a water slurry in the grinder or polisher supplied through the top platen. Cleaning water exits from nozzles 18 for cleaning the ground or polished disks. Suitable standard abrasive materials for the water slurry are available from SPEEDFAM, Inc. The ground or polished disks are then manually removed from the disk holders and inserted into a cassette.
The above described manual handling of the disks causes production delays and attendant high labor costs and can and do cause scratches and other damage, such as deformation of the disk flatness, on the disk surface by lateral and bending movements of the disks against side edges of the disk holders and the platen surfaces. These problems and effects are particularly prevalent in the unloading operations since, due to the water slurry environment of the grinding or polishing steps, the disks can be firmly adhered by surface tension or stiction to the wet lower platen surface under the disk holders. The disks have to be laterally pried up off the surface with attendant risk of causing scratches and damage to the disk(s). The result of angular random or other scratches or bending of the disks can result in imperfect manufactured disks. In use the damaged surfaces will result in having missing bits of inputted magnetic information on the disk tracks.